This invention relates to tree harvesting, and more particularly to harvesting by means of an attachment to a self-propelled steerable vehicle adapted to travel through a wooded area for harvesting selected trees.
Numerous methods and devices for tree harvesting have been previously proposed. See for example the patents identified in the accompanying "Information Disclosure Statement".
The previous concepts have included gripping a vertical tree, holding it in place, shearing it off, lowering the tree to the ground, and subsequently delimbing and cutting manually or with a separate mechanism. This procedure requires extra labor, and it is difficult to cut the delimbed tree to a reasonably uniform length. Furthermore, the tree segments end up being buried in the delimbed brush which has been removed.
Other concepts have included coming into the growing tree from the front--that is, in a direction parallel to the longitudinal vehicle axis. The tree is often then tipped and felled forwardly, thus requiring the harvester to be driven to a second location adjacent the felled tree for further operations. The closeness of adjacent growing trees in the woods may make this difficult or even impossible. U.S. Pat. No. 3,796,241 discloses a device wherein the harvester comes into the tree from the side (i.e. transverse to the vehicle's longitudinal axis), but the arrangement is such that the tree to be cut is alongside the vehicle and after the tree is cut, it must be swung into a position along the vehicle's longitudinal axis. This is cumbersome at best.
Prior shearing devices, such as chain saws, for cutting the felled tree into lengths have usually been normally positioned, when retracted, so that they will get entangled in the brush being delimbed from the trunk. Many such shearing devices cut the tree into lengths by cutting straight down vertically, with the result that the bottom edge of the trunk segment being cut will tear away as the segment is about to drop. Others, such as in U.S. Pat. Nos. 3,882,910 and 4,552,191 swing relative to the tree from a pivot disposed at a level either above the delimbing jaws or at least above the jaw openings.
Furthermore, the tree-holding jaws on many prior devices are designed to accommodate only one tree at a time. In addition, prior known delimbing jaws are able to delimb only in one direction of trunk movement.
It is an object of the present invention to provide improved concepts for harvesting trees.
In accordance with the various aspects of the invention, a tree harvester is adapted to be mounted on the front end of a steerable self-propelled vehicle, generally in line with the vehicle's longitudinal axis. The harvester includes a frame pivotable about a longitudinal axis. A telescoping boom having grab jaws at one end is mounted on the frame for pivoting between a vertical and horizontal transverse position. Delimbing jaws are fixedly mounted to the frame. When the boom is vertical and retracted, both types of jaws are in line and form a pocket which faces transversely of the vehicle and harvester axis so that the harvester can be easily steered sideways into the tree for grabbing and cutting off ahead of the vehicle. The harvester is then pivoted so that the boom and cut tree are disposed horizontally transversely and above the ground ahead of one side of the device. The boom is then extended so that the grab jaws thereon pull the cut tree trunk through the delimbing jaws. The delimbing jaws are provided with fore and aft cutting edges so that a secondary delimbing operation may be performed by retracting the boom with the cut tree trunk still intact.
The felled and delimbed trunk is cut into uniform lengths on one side of the device by a saw disposed in a protective housing adjacent the delimber jaws. The brush drops to the other side. During delimbing, the saw is normally vertical and is pivotally mounted at its lower end at a level below both sets of jaws and the tree-receiving pocket. During cutting of the trunk into lengths, the saw pivots downwardly in an arc such that the side, rather than the bottom, of the trunk is the last portion to be cut, thus preventing tearing of the cut segment before it falls to the ground.
One side of the plurality of grab jaws is center-pivoted and is rockable to efficiently accommodate more than one tree trunk at a time. An accumulator finger may also assist in this regard.